1. Introduction
There are few possible risks that can be happen in the production process. Risks can lead to the failure of reachingthe goal of production, or even can lead to a hazard. Therefore, a study is needed to understand what kind of hazard that potentially happen in the plant, and also the solution to prevent the hazard in the production processsystem by doing a risk management that cover Safety Instrumented System. One of the units that have an important role on the production process of sulphuric acid in 3rd plant of PT Petrokimia Gresik is sulphur furnace. Sulphur furnace has a function to combust molten sulphur so it results SO2 . In the operation process, there are some potential hazards that can be happen. So, a HAZOP study is needed to understand more about the potential hazard [7], and then a SIL calculation needs to be done to know the safety level of the operating SIS (Safety Instrumented System) [2]